The present invention relates generally to a molded article having an insert embedded therein, as well as an apparatus and method for making the same.
It is known to provide shoe insoles with inserts located in recesses thereof. The material of the insert generally has different characteristics from the material of the remainder of the insole to provide a specialized effect, such as a greater degree of cushioning under specific portions of the foot.
Generally, such inserts have been attached within recesses or pockets at the lower surface of a formed insole, such as by means of adhesives. However, the use of an adhesive provides various disadvantages. Specifically, it is difficult to maintain the entire insert in full contact with the insole when securing the same. This becomes even more evident as the size of the insert increases. There is thus a problem with product quality and consistency. Further, in some cases, because of the nature of materials used to form the insole, it is difficult for the adhesive to adhere to the insole. This adherence problem can also be due to the presence of mold release agent residues from the molding operation. As a result, specialized glues are required. Also, the operation requires additional labor and handling to glue the inserts, thereby increasing costs.
Several attempts have been made to mold inserts directly into insoles. Examples are described in U.S. Pat. Nos. 4,674,204 and 4,910,886. However, a problem frequently occurs with staining of the inserts from the molding material. In some cases, because of the porosity of the insert and the large pressure applied to the liquid polymer substances during the molding operation, the liquid penetrates into the insert. This results in an unsightly, non-uniform or irregular staining of the insert. The penetration of the molding polymer into the insert also changes the rigidity of the insert, that is, making it harder, and thereby changing the performance thereof.
As mentioned above, fluid polymer-forming materials sometimes tend to flow into the porous structure of the inserts due to the high pressure in the cavity. As an example, there is a chemical reaction with liquid urethanes (preferred materials for making many types of insoles), which releases a gas such as CO2. This chemical reaction causes the urethane components to expand from 120% to 200%-300% of the original volume of the liquid urethane. Since the mold is a closed mold and since the liquid urethane expands therein, there is a large increase in internal cavity pressure, so that a large external pressure must be applied to maintain the mold in a closed condition. Therefore, there is a pressure drop of about 15 to 20 psig (1.03 to 1.38xc3x97105 Newton/meter2) across the inserts, that is, from the upper surfaces of the inserts to the lower surfaces thereof. Also, the inserts are open to atmospheric pressure at their sides. Because of this, the liquid urethane flows into the cells of the porous structure of the inserts, which result in the inserts becoming more rigid and less resilient, while also causing the aforementioned staining.
In addition to the penetration through the insert, the liquid urethane tends to leak around to the underside of the insert during the molding operation, between the insert and the surface of the mold, causing a thin overcoat layer on the exposed surface of the insert around the edges of the insert. Any seals which are provided to prevent migration of the liquid urethane around the insert during the molding operation have not been very successful, and still permit this type of overflow to the underside. A reason for this overflow is the large pressure applied to the liquid urethane during the molding operation. As a result, this overflow layer provides an unsightly visual defect on the bottom surface of the insole. Because such overflow layers are not uniform, the insoles have an appearance of poor quality.
There is a further problem with such molded inserts. Specifically, it is difficult to maintain the position of the inserts during the molding operation as liquid polymer components are introduced into the mold, since the inserts tend to float on the liquid polymer.
Accordingly, it is an object of the present invention to provide a molded article having an insert embedded therein, as well as an apparatus and method for making the same, that overcomes problems with the aforementioned prior processes.
It is another object of the present invention to provide a shoe insole having a properly positioned insert embedded therein, as well as an apparatus and method for making the same, in which there is no staining or overflow layer on the inserts.
It is still another object of the present invention to provide a shoe insole having an insert embedded therein, as well as an apparatus and method for making the same, in which a retainer with an upper lip is provided around the periphery of each insert during the molding operation to provide a seal that prevents flow of the liquid urethane around the peripheral edges of the insert and also properly positions the inserts into the insert cavity of the insole.
It is yet another object of the present invention to provide a shoe insole having an insert embedded therein, as well as an apparatus and method for making the same, having an elevator mechanism that permits the inserts to be inserted into the dammed area and under the lip and thereafter clamps the peripheral edges of the inserts between the elevator mechanism and the lip to provide a seal against the flow of molding material under the insert.
It is a further object of the present invention to provide a shoe insole having an insert embedded therein, as well as an apparatus and method for making the same, in which a barrier layer may be provided on a permeable insert in order to prevent penetration of the liquid molding material into the insert during the molding operation.
It is a still further object of the present invention to provide a shoe insole having an insert embedded therein, as well as an apparatus and method for making the same, that is easy and economical to make and use.
In accordance with an aspect of the present invention, an apparatus for making a molded article containing an insert includes an upper mold half and a lower mold half for mating with the upper mold half to provide a mold cavity therein. Either mold half can include a recess, an elevator opening in a lower portion of the recess, and an inwardly directed lip at an upper portion of the elevator opening. An elevator mechanism is provided which includes a lifter for supporting an insert to be secured to the article during a molding operation, and a lifting arrangement for raising and lowering the lifter through the elevator opening such that a peripheral edge of the insert supported on the lifter is clamped between the lifter and the lip when the lifting arrangement raises the lifter.
Any lifter actuation mechanism can be used. One such lifter mechanism includes a base positioned below the lower mold half, and a cylinder mounted to the base and including a movable piston rod connected with the lifter for raising and lowering the lifter. The base includes a recess for mounting the cylinder.
In one embodiment, a retainer is removably connected to the lower mold half within the elevator opening. The retainer includes a dam flush with and removable from an inner wall defining the elevator opening, as well as the inwardly extending lip which is connected to an upper end of the darn. The retainer further includes a lower outwardly extending connector connected with a lower end of the dam and removably secured to a lower surface of the lower mold half.
In another embodiment, the lifting arrangement includes an upper slide plate having a lower inclined cam surface, the lifter being connected to the upper slide plate; a lower slide plate having an upper inclined cam surface in contact with the lower inclined cam surface; and a moving arrangement for sliding the lower slide plate relative to the upper slide plate in order to raise and lower the upper slide plate and the lifter.
Preferably, for producing shoe insoles, the lower mold half includes two such recesses corresponding to left and right insoles to be molded, one elevator opening in a lower portion of each recess, and one inwardly directed lip at the upper portion of each elevator opening. In such case, the elevator mechanism includes two lifters for supporting an insert in correspondence with each recess; and the lifting arrangement raises and lowers the two lifters such that a peripheral edge of each insert supported on each respective lifter is clamped between the lifter and the respective lip when the lifting arrangement raises the lifters.
In accordance with another aspect of the present invention, a method for making a shoe insole includes the step of providing an upper mold half and a lower mold half for mating with the upper mold half to provide a molded part cavity therein, either the lower mold half or the upper mold half including an elevator opening, and an inwardly directed lip at a cavity side of the elevator opening. Then, an insert to be secured to the shoe insole is supported on a lifter positioned in the elevator opening during a molding operation. The lifter is then moved such that a peripheral edge of the insert supported on the lifter is clamped between the lifter and the lip when the lifting arrangement moves the lifter adjacent the inwardly directed lip, and a molding material is supplied to the cavity. The mold halves are then closed while the molding material fills the cavity, and the insole is formed.
Further, according to the method, the mold halves are opened after the insole has been formed. The lifter is lowered after the insole is formed to facilitate demolding such that the peripheral edge of the insert supported on the lifter is no longer clamped between the lifter and the lip. Thereafter, the formed insole can be removed from the mold.
If the insert is a permeable material such as an open-cell foam, then a barrier layer may be provided on the insert prior to introducing the molding material in contact with the insert to prevent the molding material from penetrating through the insert. If the insert is not a permeable material, no barrier layer is usually required.
Any mechanism can be used to hold the insert in a flat position during lifter actuation, and which is removed when the insert is clamped in place. As an example, a weight may be provided having the same shape as the insert and positioned on top of the insert prior to raising the lifter in order to keep the insert flat and facilitate clamping of the insert under the lip around the entire insert periphery. The weight is removed prior to closing the mold halves together.
In accordance with still another aspect of the present invention, an insole for use with footwear includes a first layer having a lower shallow recess and a first set of properties such as cushioning, hardness, density, resilience and/or color; and an insert secured in the recess and being made of a material with a second set of properties such as cushioning, hardness, density, resilience and/or color, which may be different from the first set of properties, the insert having an upper surface secured to the first layer in the recess, and a peripheral portion of the upper surface being free and unsecured to the first layer in the recess.
Preferably, the first layer includes a forefoot portion extending generally at least to the position of the metatarsals of the foot; a heel portion; a mid portion connecting together the forefoot portion and the heel portion; an upper surface extending along the forefoot, mid and heel portions and on which a person stands; and a lower surface extending along the forefoot, mid and heel portions, the lower surface including the lower shallow recess. The insert also preferably has a barrier layer on an upper surface thereof to prevent a molding material from penetrating the insert during a molding operation. However, the present invention is not limited to full length insoles, but can be used with three-quarter length insoles, foot pads, etc.
The above and other features of the invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings.